1. Field of the Invention
The present invention relates to reduced calorie fat mimetics based on low molecular weight alkoxylated glycerol esters. More specifically, the invention relates to fat mimetics comprising glycerol which is alkoxylated such that the average number of oxyalkylene groups per molecule is no more than 5 and the number of primary hydroxyl groups converted to secondary or tertiary hydroxyl groups is between 61 percent and 95 percent based on the total number of hydroxyls on the molecule, such that the amount of primary hydroxyl groups on the molecule is between 5 percent and 39 percent of the total number of hydroxyl groups.
2. Description of the Related Art
One of the most prevalent concerns among people today is the amount of fat consumed in their daily diet. It is estimated that fat constitutes about 40% of the total calories in a western diet. Fats are consumed, for example, in meats, chocolates, sweet breads, oils and fried snacks. Conventional fats used for preparing comestible goods generally contribute around 9 calories per gram to the total caloric content of the comestible good. Thus, there is an enormous potential for a fat substitute or mimetic, which exhibits the desired characteristics of fats, but does not contribute as much as the approximately 9 calories per gram contributed by fat.
Despite the considerable research performed in the field of synthetic fat substitutes, an understanding of the precise relationship between the chemical structure of fat mimetics and digestibility remains lacking and the field remains a highly uncertain and unpredictable art. The technical literature related to fat substitutes (i.e., fat mimetics) includes conflicting observations and findings which cannot be easily reconciled or explained. Thus, in the art of fat substitutes, there is no single model or theory that may be applicable to address the digestibility and organoleptically pleasing properties for fat substitutes.
A number of fat substitutes are known which are not subject to hydrolysis and thus pass through the human digestive tract without being absorbed. One example of such a fat substitute is polyol fatty acid polyester (PPE), as shown in U.S. Pat. Nos. 3,251,827; 3,600,186 and 3,963,699. PPE is produced by the reaction of a monosaccharide, disaccharide or sugar alcohol having a minimum of four hydroxyl groups with fatty acids having from 8-22 carbon atoms. A number of methods are known for producing PPE, which basically include transesterification of the fatty acid methyl esters to the polyol. The PPE process requires long reaction time with alternating additions of fresh transesterification catalyst and excess soybean fatty acid methyl ester. In U.S. Pat. No. 3,251,827 a process for the preparation of PPE is disclosed which uses Q solvent-free interesterification using phenyl esters. U.S. Pat. No. 3,963,699 involves solvent-free transesterification to produce PPE.
Another example is U.S. Pat. No.4,861,613 to White et al. (referred to herein as "White" and incorporated by reference herein in its entirety). According to White, polyol such as glycerin must be reacted (epoxylated) with a quantity of C.sub.3 -C.sub.6 epoxide sufficient to convert greater than 95 percent of primary hydroxyl groups of the polyol to the secondary or tertiary hydroxyl groups prior to esterification with fatty acids to obtain a non-digestible fat substitute. White teaches of use of esterified epoxide-extended polyol (EEEP), having present large amounts of secondary and tertiary linkages as a non-digestible fat substitute. White requires less than 5 percent primary hydroxyl groups for resistance to hydrolysis by pancreatic lipase.
PPE and EEEP compounds possess the physical and organoleptic properties of conventional triglyceride lipids yet are significantly lower in available calories due to their pronounced resistance towards pancreatic lipase catalyzed hydrolysis. Unfortunately, as a consequence of their hydrolytic stability, low digestibility and lipophilic character, PPE and EEEP compounds which are liquid at body temperature may possess undesirable gastronomical side effects when consumed at high levels in the diet. These undesirable gastronomical side effects may include anal leakage, that is leakage of the fat substitute through the anal sphincter; and separation of the fat substitute from excreted stool.
U.S. Pat. No. 5,512,313 issued to Cooper describes esterfied propoxylated polyols containing at least 40 percent primary ester linkages and normalized hydrolysis rates of less than 20 percent based on an olive oil standard. The compounds are prepared by use of a catalyst to carry out ring-opening of a 1,2-alkylene oxide in a manner such that at least 40 percent of the hydroxyl groups of the alkoxylated polyol are primary. Cationic ring-opening polymerization catalyst is necessary to obtain at least 40 percent primary hydroxyl groups and the reaction must be carefully controlled to avoid undesired by- products such as cyclic oligomers.
U.S. Pat. No. 4,849,242 to Kershner teaches of preparation of reduced calorie food compositions containing oil-like polymer fatty acid esters having the property of being substantially hydrolyzed during the digestion process into a mixture of fatty acids and a non-caloric water-soluble or water-dispersible polymeric alcohol. U.S. Pat. Nos. 5,059,443 and 5,077,073 to Ennis describe the use of esterified alkoxylated alkyl glycosides, and esterified alkoxylated sugars and sugar alcohols as low calorie fat substitutes. These patents do not address, among other things, the use of esterified propoxylated glycerin compounds as fat substitutes, the distinction between primary and secondary or tertiary ester linkages on the digestibility of the fat substitute or the effect of partial digestibility on the undesirable gastrointestinal side effects that may occur with some fat substitutes.
U.S. Pat. No. 5,597,605 issued to Mazurek concerns low calorie fat components of food that consist of esterified propoxylated glycerin compounds and a partially digestible liquefying agent with particular solid fat index (SFI) profiles. These low calorie fat components are reported to lack undesirable gastrointestinal side effects as a result of high solids content of the EPG while maintaining satisfactory organoleptic properties partially due to the liquefying agent. U.S. Pat. No. 5,376,398 to Cooper involves the use of fatty-acid esterified polytetramethylene ether glycols with edible triglycerides.
Applications of the assignee of the invention involving the replacement of conventional fat in comestible products with fatty acid-esterified propoxylated glycerin compositions are currently pending. These applications involve the use of fatty-acid esterified propoxylated glycerin compositions in milk products, Reduced Calorie Reconstituted Milk and Milk Products, Ser. No. 08/572,277 filed on Dec. 13, 1995; fried snack foods, Reduced Calorie Fried Snacks, Ser. No. 08/575,711 and Reduced Calorie Fried Snacks Having a Cooling Sensation When Placed in the Mouth, Ser. No. 08/575,373 both filed on Dec. 20, 1995 and spoonable dressings, Freezable Low-Calorie Spoonable Dressings and Method for Their Production, Ser. No. 09/262,221, filed on Mar. 4, 1999.
It has now been found that by limiting the degree of propoxylation of polyols and the number of primary hydroxyls that are converted to secondary or tertiary hydroxyls, the undesirable gastronomical side effect of anal leakage can be overcome. A new class of reduced calorie fat mimetics has now been discovered in which glycerol is partially alkoxylated, such that the average number of oxyalkylene groups per molecule is no more 5, and more particularly between about 2 and 5, and subsequently esterified with fatty acids. This level of alkoxylation limits the number of primary hydroxyl groups that are converted to secondary or tertiary hydroxyl groups to between about 61 percent and 95 percent. When the total number of primary hydroxyl groups on the molecule are between 5 percent and 39 percent, the undesirable gastrointestinal side effects are alleviated. Since primary hydroxyl esters are significantly more sensitive to lipase activity than secondary/tertiary hydroxyl esters, these compounds are hydrolyzed to a greater degree in vivo than, for example, the EEEP compounds of White. The fat mimetic compositions of the present invention are partially digested in vivo and hydrolysis increases the hydrophilicity of the compounds. As a result, oil intolerance and anal leakage are reduced and/or obviated by the partial digestibility of the fat mimetic which makes the compound more polar and less oil like. This feature of the invention, that is the propoxylation number being no more than 5 and the number of primary hydroxyl groups converted to secondary or tertiary being between 61 percent and 95 percent such that the amount of primary hydroxyl groups is between 5 percent and 39 percent, allows for the creation of emulsions in the lower bowel during digestion which aids in the reduction and/or prevention of anal leakage.
In the present specification and claims, all parts and percentages are by weight unless otherwise specified.